I would use a splitter for the subwoofer and the speakers; I usually get a bit creative. Although a quick search about low/high level outputs confused me more than it helped, I'll look up all the details before I buy any new speakers (that's why I'm posting here anyway).
I'm not sure how using splitters may diminish quality but, seriously now, I'm using the Logitech z333 speakers and I find their quality just fine for my needs, so while you may consider them garbage, I don't need an expensive, amazing system. I'm just a cheap bastard trying to get something that will sound good to me.